Management of pure mucocele-like lesion (MLL) diagnosed on percutaneous breast biopsy (PBB) is controversial. To assess surgical upgrade rate and clinical outcome of pure MLL obtained as sole diagnosis on PBB. Patients diagnosed with a MLL as the most advanced lesion on PBB from April 1997 to December 2010 were reviewed for radiologic presentation, biopsy technique, and pathologic and clinical outcomes. Of the 21,340 image-guided PBB performed during the study period, 50 women with 51 MLL (0.24%) were identified. Mean age was 53.1 ± 7.7 years. Radiologic findings were mostly microcalcifications (n = 47, 92.2%). Stereotactic PBB was performed for 49 lesions (96.1%). Surgery was performed shortly after biopsy in 35 women, with benign final pathology in 33, and upgrade to ductal carcinoma in situ (DCIS) in two patients (2/35, 5.7%). Mean follow-up was 4.2 ± 2.5 years (3.7 ± 2.1 years for surgical patients; 5.9 ± 2.9 years for follow-up only patients); three women were lost to follow-up (3/50). Three invasive cancers (3/47, 6.4%) were diagnosed 1.2, 1.2, and 2.8 years after biopsy: two in surgical patients, and one in a follow-up only patient. No cancer occurred at the same site as the original MLL. Pure MLL lesion of the breast is a rare entity and is mostly associated with a benign outcome. We observed an upgrade to DCIS slightly superior to 5%, but no invasive cancer. It is therefore unclear if these lesions should be excised or clinically and radiologically followed up when such lesions are found at PBB.